This invention concerns building and concrete construction generally, and more particularly assembly and stripping of concrete forms made of light gauge sheet material with or from form support brackets and associated equipment.
Generally, time and motion observations of erection and stripping of braced or stayed formwork have suggested that although semi-permanent, threaded, metal-to-metal connection means such as nuts and bolts, Allen screws, wingnuts and the like may be advantageously used in place of welding to hold subparts of formwork support assemblies together, when such joining means are used to make repetitive connections in the field, such as those between forms and formwork supports, on-site assembly and stripping of said formwork becomes non-competitive with timber methods, at least partly because of the rapidity and convenience of nail-fixing. It is proposed therefore, that threaded joining means (nuts, bolts, screws and the like) be reserved for connections not routinely pulled apart in the field, and that new application of rapid-cycling metal-to-metal connections be used for repetitive joining of formwork components on site.
In order to compete with the speed and convenience of nail fixing, it has been necessary to borrow from other technologies where rapid field cycling of metal connections is routine.
From weapons technology a suitably simple, robust and well known example is the century-old Mauser rifle action wherein a pair of forward mounted locking lugs, monolithic or one-piece with a multifunctional firing pin carrier or "bolt" capable of rotation about an axis orthogonal to the major plane of the "bolt-face" are inserted--at a particular arrested alignment of said rotation--through a "gate" into a housing or receiver, the latter being mounted rearward of, but functionally monolithic with the barrel; then the pair of locking lugs are caused to rotate (most commonly, forty-five degrees clockwise) within the housing and away from the gate alignment to the locked-action position. Advantages of such a connection in metal formwork applications include; speed, as such a connection can be made and broken considerably faster than nail fixing/extraction, and security, as a force acting orthogonally against either the plane of the "bolt" face or form face has virtually no vector component (in parallel planes such as a theoretical rotational plane of centre-line of locking lugs) acting to unlock the assembly.